Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/043—Analysing solids in the interior, e.g. by shear waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
  • G01N29/0609—Display arrangements, e.g. colour displays
  • G01N29/0645—Display representation or displayed parameters, e.g. A-, B- or C-Scan
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
  • G01N29/0654—Imaging
  • G01N29/069—Defect imaging, localisation and sizing using, e.g. time of flight diffraction [TOFD], synthetic aperture focusing technique [SAFT], Amplituden-Laufzeit-Ortskurven [ALOK] technique
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/22—Details, e.g. general constructional or apparatus details
  • G01N29/225—Supports, positioning or alignment in moving situation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/22—Details, e.g. general constructional or apparatus details
  • G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
  • G01N29/262—Arrangements for orientation or scanning by relative movement of the head and the sensor by electronic orientation or focusing, e.g. with phased arrays
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/22—Details, e.g. general constructional or apparatus details
  • G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
  • G01N29/265—Arrangements for orientation or scanning by relative movement of the head and the sensor by moving the sensor relative to a stationary material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/02—Indexing codes associated with the analysed material
  • G01N2291/023—Solids
  • G01N2291/0234—Metals, e.g. steel
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/042—Wave modes
  • G01N2291/0421—Longitudinal waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/042—Wave modes
  • G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/04—Wave modes and trajectories
  • G01N2291/056—Angular incidence, angular propagation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/10—Number of transducers
  • G01N2291/102—Number of transducers one emitter, one receiver
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/10—Number of transducers
  • G01N2291/106—Number of transducers one or more transducer arrays
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/26—Scanned objects
  • G01N2291/263—Surfaces
  • G01N2291/2634—Surfaces cylindrical from outside
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/26—Scanned objects
  • G01N2291/267—Welds
  • G01N2291/2675—Seam, butt welding

Definitions

• the present invention relates generally to non-destructive testing, and relates more specifically to a method for detecting and characterizing defects in a tubular pipe.
• Such a process is applicable in many industrial sectors including, and not limited to: electricity production, petrochemicals, chemistry, the food industry, and more generally, industries operating with fluids circulating in tubular steel pipes. welded.
• Tubular pipes are generally made up of several portions linked together by junctions. These junctions may in particular be welds.
• a tubular steel pipe transporting fluid is subject to strong stresses, especially when these tubular pipes undergo significant temperature and pressure variations, and also chemical attacks transported by fluids (gas, water, hydrocarbons, etc.). Defects, called fatigue defects, may appear, resulting in cracks in the pipe material. It should be noted that only the exterior of the pipe is generally accessible, and that checks must be able to be carried out from this exterior only. Numerous non-destructive testing methods have been developed to detect these fatigue defects, and in particular methods using ultrasonic waves.
• stress corrosion cracks are branched cracks with very little opening, and especially extend from inside the pipe, near a welded junction between two portions of the pipe. tubular pipe.
• characterization we mean the location of an FCS and the determination of the height of an FCS, that is to say its radial extension from the inside of the pipe. It is desirable to be able to reliably characterize the FCS even when they have a low height, for example a few millimeters, in order to be able to anticipate a deterioration of the pipe. Such sensitivity is all the more difficult as control by means of ultrasonic waves from the outside requires said ultrasonic waves to pass through the entire thickness of the wall of the tubular pipe.
• Austenitic stainless steels are steels that have a coarse microstructure (high grain size). These different elements generate significant structural noise and attenuate the propagation of the ultrasound beam, which makes the use of ultrasound complex.
• a method for detecting and characterizing a stress corrosion crack in a tubular steel pipe at an inspection zone extending from a welded junction between two portions of the tubular pipe. by means of an ultrasonic probe comprising: a) for a plurality of measuring positions distributed circumferentially around the tubular pipe on an exterior surface of the tubular pipe at the welded junction: al) positioning of the ultrasonic probe measurement against the surface external to the measuring position, the measuring probe having an emission surface making an angle of between 10° and 30° relative to a plane tangent to the external surface of the tubular pipe supporting the measuring probe , a2) successively transmitting and receiving at least two bursts of ultrasound of the same frequency to obtain a plurality of measurement signals, a first burst in direct mode plane wave being configured to scan a first area of interest encompassing the inspection area and the welded joint with a beam axis scanning a scanning angular range at least 10° greater than an angular range of interest occupied by the zone of interest relative to a plane tang
• the plurality of bursts comprises at least one burst in indirect mode in plane waves and at least one burst in indirect mode in spherical waves, the second construction being obtained from at least one of the burst in indirect mode in plane waves and the burst in indirect mode in spherical waves;
• the plurality of bursts includes a burst in direct mode and plane waves whose region of interest extends over the entire thickness of the pipe, including the interior surface driving;
• the trace of a stress corrosion crack has a first amplitude peak with a maximum amplitude greater than at least 1.5 times a maximum amplitude of the second amplitude peak;
• the trace of a stress corrosion crack has an amplitude trough separating the first amplitude peak and the second amplitude peak, with a minimum amplitude less than 1.5 times the maximum amplitude of the second peak ;
• the first amplitude peak corresponds to a foot of the stress corrosion crack opening onto the internal face of the tubular wall, and the second amplitude peak corresponds to a head of the stress corrosion crack opposite the foot of the crack ;
• step c) the trace of a stress corrosion crack is searched in a search zone likely to contain traces of stress corrosion crack, this search zone being located by means of the trace of the stress corrosion crack penetration echo, or by means of the trace of the transition zone;
• the measuring probe is carried by a movable assembly on a collar extending over and around the welded junction, and placing the measuring probe at a measuring position among the plurality of measuring positions distributed circumferentially around of the tubular pipe comprises the movement of the movable assembly along the collar to said measurement position;
• the mobile assembly comprises a carriage configured to be moved along the collar and an instrument holder configured to couple the carriage and the measuring probe;
• the instrument holder comprises at least one index wheel configured to rotate as the carriage moves along the collar around the tubular pipe, associated with an indexing sensor capable of quantifying the rotation of the wheel index, and the emission of bursts of ultrasonic waves is conditioned by index information recorded by the indexing sensor.
• the invention also relates to a computer program product comprising program code instructions for executing the steps of the method according to the invention, in particular steps b), c) and d), when said program is executed on a computer.
• the computer program product may take the form of a non-volatile medium on which the instructions are stored.
• FIG. 1 is a diagram showing steps of the process according to a possible embodiment of the invention.
• FIG. 2 schematically shows a measuring probe near a welded junction between two portions of the tubular pipe, according to a possible embodiment of the invention
• FIG. 3 schematically shows the relative orientations of two sets of transducer elements of the ultrasonic measuring probe, according to a possible embodiment of the invention
• FIG. 4a shows an overview of a collar of a wearer of the measuring probe, according to a possible embodiment of the invention
• FIG. 4b shows an example of a clasp of the necklace of Figure 4a, according to a possible embodiment of the invention
• FIG. 5 shows an example of a carriage of a carrier of the measuring probe, according to a possible embodiment of the invention
• FIG. 6 shows an overview of an example of carrier, according to a possible embodiment of the invention.
• FIG. 7 shows an overview of an instrument holder of a carrier of the measuring probe, according to a possible embodiment of the invention
• FIG. 8 schematically shows the emission of a first burst of ultrasound, according to a possible embodiment of the invention
• FIG. 9 schematically shows the emission of a second burst of ultrasound or a third burst of ultrasound, according to a possible embodiment of the invention.
• FIG. 10 schematically shows the emission of a fourth burst of ultrasound, according to a possible embodiment of the invention
• - Figure 11 shows examples of representations resulting from a construction from measurement signals
• FIG. 12 shows examples of representations resulting from a construction from measurement signals
• FIG. 13 shows two amplitude peaks of the trace of a stress corrosion crack appearing as a localized variation of amplitude in a representation.
• a method of detecting and characterizing a stress corrosion crack in a tubular steel pipe 2 will be described, at the level of a welded junction 3 between portions 2a , 2b of the tubular pipe 2.
• a molten zone 3a, or weld bead is present between the respective ends of the portions 2a, 2b of the tubular pipe 2.
• a first SOI step consists of carrying out measurements for a plurality of positions of measurement distributed circumferentially on an exterior surface of the tubular pipe at the level of a welded junction 3 between two portions 2a, 2b of the tubular pipe by means of an ultrasonic measuring probe 1.
• step 1 For each measurement position, it is appropriate to first place the ultrasonic measuring probe 1 (SOI step 1) against the exterior surface at the measuring position, then successively emit and receive at least two bursts of ultrasound of the same frequency to obtain a plurality of signals measurement (step S012) at this measurement position.
• the ultrasonic measuring probe 1 is arranged against the outer surface 2a of the tubular pipe 2 at a measuring position.
• the ultrasonic measuring probe 1 has an active emission surface 4 making an angle of between 10° and 30° relative to a plane tangent to the exterior surface 2a of the tubular pipe 2 supporting the ultrasonic measuring probe 1.
• the ultrasonic measuring probe 1 comprises a shoe 6 comprising an interface surface 6a in contact with the exterior surface of the tubular pipe, and an inclined plane (typically with an angle between 10° and 30° relative to the interface surface) on which is arranged the active emission surface 4 of the ultrasonic measuring probe 1, comprising sets of ultrasonic transducers 8.
• a coupling medium such as water can be placed between the surface of interface 6a of the shoe 6 and the exterior surface of the tubular pipe.
• the shoe 6 can be made of any material allowing both the maintenance in position of the transducers ultrasonic 8 and the transmission of ultrasonic waves through the shoe 6.
• the shoe can be made of cross-linked polystyrene.
• the ultrasonic measuring probe 1 is configured so as to highlight the trace of a stress corrosion crack appearing as a localized variation in amplitude in a representation resulting from the measurement signals, the trace presenting two distinct amplitude peaks . To do this, it is possible to vary several parameters of the measuring probe 1, depending on the equipment used. Below are some parameters that can achieve good results, although these do not necessarily have to be required for the implementation of the process.
• the ultrasonic measuring probe 1 is configured to emit bursts of ultrasonic waves at a frequency between 2 and 10 MHz, and preferably between 2 and 7.5 MHz.
• the ultrasonic measuring probe 1 is multi-element and comprises two sets 8a, 8b of transducer elements aligned in the form of strips, as illustrated in Figure 3. In use, one strip 8a is used in transmission while the The other strip 8b is used in reception.
• the two bars 8a, 8b can be separated by 2 to 10 mm, and preferably by 0.5 mm to 3.5 mm.
• the bars are arranged to obtain a refracted angle of between -10° and 70°, in an austenitic steel with an approximate speed of the ultrasonic waves of 5700 m/s, after a path in the shoe 6 of between 10 mm and 30 mm.
• the strips 8a, 8b can for example each comprise between 32 and 34 transducer elements.
• the pitch between the transducer elements can be, for example, between 0.6 mm and 1 mm.
• the bars 8a, 8b are not arranged on the same plane, nor parallel.
• the strips 8a, 8b can be arranged with a bigle angle P, or “squint angle” in English, which can be approximated by half the angle formed by the alignments of transducer elements of each strip.
• the bigle angle P can be between 0.1° and 3°.
• the bars 8a, 8b can have a roof angle a, that is to say a half-angle formed by the axes of the two acoustic beams, between 1.25° and 3.25°.
• the two phases of the measuring step are repeated several hundred times, the number of measuring positions being preferably greater than 100 around the welded junction 3.
• a probe carrier 10 as illustrated in Figure 6 and detailed in Figure 4a, 4b, 5, and 7.
• the purpose of the probe carrier 10 is to carry the measuring probes 1 so that said measuring probes 1 can be movable on and along the probe carrier 10.
• the probe carrier 10 is placed around the control zone on the outskirts or on the welded junction 3, thus surrounding the tubular elements.
• the carrier 10 comprises several elements: a circular collar 12 enclosing the tubular pipe 2, and a movable assembly along the collar, which may in particular comprise a carriage 14 configured to be moved along the collar 12 and an instrument holder 16 configured to couple the carriage 14 and the measuring probe 1.
• Figure 4a shows an example of a circular collar 12 intended to be mounted around the perimeter of the tubular pipe 2 and to enclose it.
• the collar 12 is articulated, comprising several sections 12a, 12b, 12c in the shape of arcs of a circle connected in pairs by pivot connections, as well as a clasp 18 comprising several closing positions.
• Figure 4b shows an example of clasp 18.
• a section 12b of the collar is extended by an arm 20 carrying at its end a crosspiece 22 transverse to the arm 20.
• Another section 12a of the collar comprises housings 24 configured to receive the crosspiece 22 after a radial insertion thereof and hold it against circumferential traction.
• the housings 24 are distributed in several circumferential positions, allowing tightening adapted to the external diameter of the tubular pipe 2 by offering closing positions for several diameters.
• Figure 5 shows an example of a carriage, comprising at least two curved portions 14a, 14b connected by a joint 26, typically establishing a pivoting connection.
• a locking member 28 straddling the two curved portions 14a, 14b can be actuated by a control member 30 which can also act as a handle for movement.
• Other dedicated handles 32 may be provided.
• the locking member 28, preferably a pneumatic cylinder can move from an unlocking position in which the two curved portions 14a, 14b are movable thanks to the articulation 26 to a locking position in which the articulation 26 is locked, preventing relative movement between the two curved portions 14a, 14b.
• the articulation 26 is left movable by the locking member 28, and the internal faces of the curved portions 14a, 14b are arranged against the external face of the collar 12.
• the joint 26 is then locked by the locking member 30.
• the carriage 14 also includes wheels 34 dimensioned to be in contact with the external face of the tubular pipe 2 when the carriage 14 is in place on the collar 12 enclosing this external face of the tubular pipe 2.
• the carriage 14 and the instrument holder 16 are configured so that the instrument holder 16 is mounted integral with the carriage 14.
• the movement of the carriage 14 therefore causes the movement of the instrument holder 16.
• the instrument holder 16 comprises at least one support arm 36 configured to receive an ultrasonic measuring probe 1 on brackets 38 for fixing said support arms 38, offset relative to the welded junction 3.
• the instrument holder 16 includes a supporting arm 36 on each side of its circumferential direction of movement.
• the instrument holder 16 also comprises at least one index wheel 40, 42, configured to rotate as the carriage 14 moves along the collar 12 around the tubular pipe 2, associated with an indexing sensor adapted to quantify the rotation of the index wheel 40, 42.
• the instrument holder 16 comprises two index wheels 40, 42: a first wheel 40 configured to roll on the tubular pipe 2 and intended for marking on the curvilinear abscissa during the circular movement of the instrument holder 16, and a second wheel 42 configured to roll on a guide 43 between a central portion of the instrument holder 16 to the arm 36 in order to determine an axial offset (along the main axis of the tubular pipe at the level of the welded junction 3) of this arm 36 and therefore of the measuring probe 1 carried by this arm 36 relative to the welded junction 3.
• a first wheel 40 configured to roll on the tubular pipe 2 and intended for marking on the curvilinear abscissa during the circular movement of the instrument holder 16
• a second wheel 42 configured to roll on a guide 43 between a central portion of the instrument holder 16 to the arm 36 in order to determine an axial offset (along the main axis of the tubular pipe at the level of the welded junction 3) of this arm 36 and therefore of the measuring probe 1 carried by this arm
• the measuring probe 1 is not located radially facing the welded junction 3 or the inspection zone extending from it in which are likely to be the FC S.
• the measuring probe is arranged so as to encompass in an oblique scan a zone of interest 44 encompassing the inspection zone and the welded junction 3, and is therefore offset relative to these .
• the measuring probe 1 can be moved successively between the measuring positions around the circumference of the pipe tubular 2.
• the rotational movement can be caused manually by pushing on a handle 32, or a motorization can be provided to move the carriage 14 along the collar 12, for example by motorizing the wheels of the carriage 14.
• the index wheel 40, 42 makes it possible to determine that a new measurement position has been reached, typically after a predetermined distance has been covered (typically 1 to 3 mm), and the sensor sends information index to the measuring probe 1 or to a control unit to which the measuring probe 1 is connected, in order to cause the emission of bursts of ultrasound at this measuring position.
• the emission of bursts of ultrasonic waves is thus conditioned by the index information recorded by the indexing sensor. Therefore, it is sufficient to make the mobile assembly travel around the circumference of the tubular pipe 2 along the collar 14 to travel through the plurality of measurement positions distributed circumferentially on an exterior surface of the tubular pipe 2, and acquire the corresponding measurement signals.
• the measuring probe 1 successively transmits and receives at least two bursts of ultrasound of the same frequency to obtain a plurality of measuring signals.
• at least three bursts of ultrasound are successively transmitted and received, and more preferably at least four bursts of ultrasound are successively transmitted and received.
• four bursts of ultrasound are successively transmitted and received. The order of the bursts is given for information purposes only, and can be modified.
• a first burst emits in a longitudinal plane wave in direct mode (i.e. only considering a direct round trip of the ultrasonic waves between the transducer elements in the region of interest, without taking into account possible additional path linked to bounces and associated with 1 or more changes in ultrasound propagation mode) and is configured to scan a first zone of interest 50 with a beam axis scanning a greater scanning angular range of at least 10° at an angular range of interest occupied by the first zone of interest 50 relative to a plane tangent to the exterior surface of the tubular pipe 2 supporting the measuring probe 1.
• the first zone of interest 50 is centered on a zone 54, located between the welded junction 3 and the measuring probe 1, where the FCS are likely to be located, and on the one hand follows the contours of a portion of the tubular pipe at the level of the welded junction 3, and s extends a few millimeters from the latter in said portion of tubular pipe 2, typically over a distance which can range from 5 mm to 20 mm from the molten zone 3 a.
• the first zone of interest 50 also extends from the interior of the tubular pipe 2, a few millimeters (typically between 5 and 10 mm) from the internal surface 52 of the tubular pipe 2, up to a height of at least 15 mm, and preferably at least 20 mm in the thickness of the wall of the tubular pipe 2.
• the first zone of interest 50 crosses the welded junction 3.
• the first zone of interest 50 can be located at a location between the angles 45° and 60° relative to a plane tangent to the exterior surface 5 of the tubular pipe 2, from the penetration of the ultrasonic waves in the wall of the tubular pipe 2, which is referred to as the angular range of interest.
• the transducer elements are then controlled to emit ultrasound by scanning an angular scanning range thanks for example to emission delays between them. Scanning is understood as the movement of a beam axis corresponding to an axis of highest ultrasound intensity or to a median axis of the emitted ultrasound beam.
• This scanning angular range extends on either side of the first angular range of interest 50, preferably by at least 5° on each side of the angular range of interest, and more preferably by at least minus 10°.
• a scanning angular range can be between 28° and 70° with an angular step between 1° and 3°.
• a second burst of ultrasound is emitted, with plane waves in indirect mode sweeping across the scanning angular range.
• the waves can then be transverse, or longitudinal or a combination of the two.
• the flight time of the waves is longer, which results, as illustrated in Figure 9, by taking into account waves having undergone multiple reflections, and in particular by taking into account waves having undergone reflection on the internal surface of the tubular pipe.
• the second zone of interest 56 then encompasses and extends the first zone of interest in a distal direction opposite the measuring probe 1.
• a third burst of ultrasound is emitted according to the same methods as the second burst of ultrasound, with however spherical waves rather than plane waves.
• the second ultrasound burst and the third ultrasound burst serve to distinguish FCS from other artifacts in the measurement signals 1, and are complementary.
• a fourth burst of ultrasound, illustrated in Figure 10, in direct mode, is this time centered on a fourth zone of interest 58 extending below the measuring probe 1, over the entire thickness of the wall of the tubular pipe 2, and more precisely from the shoe 6 of the measuring probe 1 to more than one thickness of the wall beyond the internal surface 52 of the wall of the tubular pipe.
• this fourth area of interest 58 does not reach the welded junction 3.
• This fourth burst is used to take into account the echoes from the shoe-pipe interface (in order to determine the coupling), the background echoes on the internal surface 52 of the pipe wall tubular 2, and their repetitions, in order to be able to determine the attenuation of the ultrasound.
• a reconstruction of a first representation is carried out from the first bursts in which a characteristic zone of the welded junction 3 appears.
• at least one other representation is also carried out from the measurement signals of the second bursts, and where the third bursts.
• a reconstruction is carried out for each of the other bursts: we thus have a construction of a representation from the second bursts, a construction of a representation from the third bursts and a reconstruction of a representation from the fourth gusts.
• the reconstructions of the different representations from the different bursts of ultrasound can be done with or without mode conversion, that is to say by exploiting the transition from a longitudinal mode to a transverse mode or vice versa, as is practiced and well known to the state of the art.
• mode we mean the mode of propagation of ultrasound: a longitudinal mode which corresponds to the main direction of propagation of the ultrasound wave, and a transverse mode which is normal to the longitudinal mode.
• the reconstruction is done by the total focusing method, or TFM, which consists of systematically applying the basic focusing principle of multi-element ultrasound in a defined region of interest.
• the region of interest is segmented into a grid of positions, or “pixels,” and phased array focusing is applied to each pixel in this grid.
• TFM makes it possible to generate a representation of the region of interest which is focused everywhere and at all depths.
• Figures 11 and 12 show examples of representations thus obtained.
• the representations are sets of two-dimensional data associating an amplitude with a location in a two-dimensional space. Representations can therefore take the form of images, as in these figures.
• Figure 11 shows for example a first representation 100 obtained from the first bursts, along a plane transverse to the welded junction (T-scan), and therefore perpendicular to the circumference of the pipe.
• T-scan welded junction
• the trace of the penetration echo is therefore a characteristic zone of the welded junction 3.
• a transition zone 108 between a wall of the tubular pipe 2 and a molten zone 3a of the welded junction 3
• said trace of the transition zone 108 appearing as an amplitude variation line which follows the geometry of the end of the portion 2a of the tubular pipe 2.
• the trace of the transition zone 108 is also a characteristic zone of the welded junction 3.
• Other characteristic zones of the welded junction 3 can be highlighted, as long as they appear in a representation even in the absence of a defect.
• a search area 110 likely to contain traces of stress corrosion cracks has been circled in dotted lines. It is in this search zone 110 that a possible trace of a stress corrosion crack appearing as a localized variation in amplitude in the first representation is sought.
• the search zone 110 extends in a portion 102 from its end to a distance extending between 5 and 20 mm in the portion 102.
• the penetration echo trace 106 makes it possible to know the position of the welded junction between two portions of the tubular pipe, and therefore to locate, in the first representation, the zone 110 likely to contain FCS.
• Figure 10 also shows another representation 112 constructed from the first bursts, but according to a different plan since it is here a C-scan, corresponding to an unrolling of the internal surface of the tubular pipe, where distinguishes the weld bead 114 appearing as an alignment of traces.
• Search zone 116 likely to contain FCS has been surrounded by dashes.
• Figure 12 shows another example, with a first representation 200 obtained from the first bursts, along a plane transverse to the welded junction (T-scan). There we find the contour of the ends of the two portions 202, 204 coupled by the welded junction 3, and the penetration echo trace 206 making it possible to locate the search zone 210 likely to contain traces of stress corrosion cracks.
• the first representation 200 and the C-scan 212 are from the first bursts, and therefore come from direct mode waves.
• At least one other representation (designated as a second representation) is constructed from bursts other than the first bursts, said other bursts being in indirect mode. These are typically the second bursts and/or third bursts. This other representation serves to distinguish the trace of the corrosion crack among the artifacts.
• a second T-Scan representation 230 and a second C-scan representation 240, which can be constructed from the second bursts or the third bursts, or by combining the measurement signals of the second bursts and the third bursts, and for example by subtracting them.
• a trace of a stress corrosion crack appears as a localized variation in amplitude in the first representation and the second representation, with the trace exhibiting two amplitude peaks in the first representation. If a localized variation in amplitude does not appear in the second representation 230, 240, then a localized variation in amplitude in the first representation is not identified as a trace of a stress corrosion crack.
• the measurement signals resulting from bursts in indirect mode are less sensitive to possible artifacts, and therefore make it possible to distinguish traces of stress corrosion cracks among other artifacts.
• a height of the corrosion crack can be determined from a distance between the two amplitude peaks of the trace (step S04).
• Figure 13 shows, at the bottom, an example of a trace 240 of a stress corrosion crack identified in a first cross-plane representation.
• the local variation in amplitude of the trace 240 comprises two distinct parts: a first part 242, greater in both amplitude and surface area, and a second part 244, less important both in amplitude and surface area. .
• the first part 242 of the trace 240 corresponds to the foot of the stress corrosion crack, that is to say the part of the crack which opens onto the internal face of the tubular pipe, while the second part 244 of the trace 240 corresponds to the head of the stress corrosion crack, that is to say the part of the deepest crack in the wall, and therefore the furthest from the internal face 52 of the tubular pipe.
• a graph 250 showing the amplitudes corresponding to trace 240.
• the first amplitude peak 252 has an amplitude greater than the second amplitude peak 254, typically with a maximum amplitude of the first amplitude peak 252 greater than the maximum amplitude of the second amplitude peak 254, and preferably at least 1.5 times greater than the maximum amplitude of the second amplitude peak 254, and preferably at least twice greater.
• the amplitudes here are not necessarily directly amplitudes of the measurement signals, but can be any indicator linked to the energy of the measurement signals.
• the various parameters of the measuring probe can be modified in order to reveal preferential characteristics on trace 240.
• it is sought to reveal a maximum of energy on the head of the crack this is that is to say that we seek to obtain a very pronounced first peak of amplitude 252.
• the distance between the two amplitude peaks 252, 254 of trace 240 it is possible to determine the distance between the respective maximums of these amplitude peaks 252, 254.
• the distance between the two amplitude peaks 252, 254 of trace 240 is directly linked to the height of the crack, that is to say to the depth of the crack between its foot and its head. Knowing the height of the stress corrosion crack makes it possible to characterize the stress corrosion crack, and therefore to evaluate the significance of this stress corrosion crack in terms of the mechanical strength of the tubular pipe.

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